Sendmail Installation and Operation Guide
SMM:08-27
/canon hostname try to canonify hostname.
/map mapname key
look up `key' in the indicated `mapname'.
/quit
quit address test mode.
3.9. Persistent Host Status Information
When HostStatusDirectory is enabled, information about the status of hosts is maintained on
disk and can thus be shared between different instantiations of sendmail. The status of the last con-
nection with each remote host may be viewed with the command:
sendmail -bh
This information may be flushed with the command:
sendmail -bH
Flushing the information prevents new sendmail processes from loading it, but does not prevent
existing processes from using the status information that they already have.
4. TUNING
There are a number of configuration parameters you may want to change, depending on the
requirements of your site. Most of these are set using an option in the configuration file. For example,
the line "O Timeout.queuereturn=5d" sets option "Timeout.queuereturn" to the value "5d" (five days).
Most of these options have appropriate defaults for most sites. However, sites having very high
mail loads may find they need to tune them as appropriate for their mail load. In particular, sites experi-
encing a large number of small messages, many of which are delivered to many recipients, may find
that they need to adjust the parameters dealing with queue priorities.
All versions of sendmail prior to 8.7 had single character option names. As of 8.7, options have
long (multi-character names). Although old short names are still accepted, most new options do not
have short equivalents.
This section only describes the options you are most likely to want to tweak; read section 5 for
more details.
4.1. Timeouts
All time intervals are set using a scaled syntax. For example, "10m" represents ten minutes,
whereas "2h30m" represents two and a half hours. The full set of scales is:
s
seconds
m
minutes
h
hours
d
days
w
weeks
4.1.1. Queue interval
The argument to the -q flag specifies how often a sub-daemon will run the queue. This is
typically set to between fifteen minutes and one hour. If not set, or set to zero, the queue will
not be run automatically. RFC 1123 section 5.3.1.1 recommends that this be at least 30 minutes.
Should you need to terminate the queue jobs currently active then a SIGTERM to the parent of
the process (or processes) will cleanly stop the jobs.
4.1.2. Read timeouts
Timeouts all have option names "Timeout.suboption". Most of these control SMTP oper-
ations. The recognized suboptions, their default values, and the minimum values allowed by